Appararus and method for creating three-dimensional modeling data from an object

ABSTRACT

A method and apparatus for the creation of a electronic domain geometric modeling data file containing internal and external features of an object of interest by first successively removing contours of material forming the object to form exposed surfaces and thereby reveal the internal and external features contour by contour and second by subsequently, successively acquiring data relative to the exposed surfaces is provided. The geometry of each exposed surface is obtained, processed and recorded after each contour is removed. The processing is converted to perimeter data to define the internal and external features and surfaces of the object and the perimeter data is combined to yield a three dimensional electronic domain representation of the object. If desired this representation can be displayed on a computer monitor or printed onto paper. In a representative embodiment of the present invention a face mill is provided to remove the contours, a scanner is used to obtain the data relative to the exposed surfaces, and a shuttle is used to transport the object between the mill and the scanner for alternating steps of material removal and scanning.

This application is a continuation-in-part of application Ser. No.08/284,253, filed Aug. 2, 1994, now U.S. Pat. No. 5,621,648.

FIELD OF THE INVENTION

The present invention relates in general to method and apparatus forproducing an electronic representation of an object. In particular, thepresent invention relates to an apparatus and a method for selectivedestruction of an object and its reproduction in computer memory andassociated displays as well as in a hard copy form, such as paper.

BACKGROUND OF THE PRESENT INVENTION

There exist known methods for producing three dimensional images in anelectronic domain from solid physical objects. Typically, these methodsinvolve some form of data acquisition of information relative to theexterior surfaces of the object, either by contact or non-contact means.The result is a computer generated image of the exterior surface of theobject. For example, one such method involves physical contactcoordinate measuring methods. This particular method can produceaccurate physical part dimensions, but is deficient because it is timeconsuming to use because of the amount of data generated and because itcannot readily secure interior features of the object. Non-contactmethods such as laser scanning are also capable of creating accuratepart dimensions, but like the coordinate measuring methods are notreadily capable of capturing internal part features. Interior features,such as surface geometries and structural elements cannot readily becaptured by these methods and so they are of limited use.

There do exist methods and apparatus for capturing both internal andexternal features of a physical object. This is a desired and soughtafter ability both from the stand point of quality control ofmanufactured parts and because of the desire to be able to reverseengineer objects. Among the methods utilized for these ends are thenon-destructive techniques of ultrasound imaging and computed tomography(CT). Ultrasound imaging is generally not accurate for reproducingphysical measurements with the desired accuracy. While CT can producemodeling data of the desired accuracy, the equipment used to performthis type of operation or inspection is often quite expensive, withcosts for the x-ray producing equipment, the housing for the equipment,the sensors for detecting the x-rays, and the computer resourcesnecessary to operate the CT system often raising the cost to a figure inthe one million dollar range. In addition, CT presents a radiationhazard and requires special facilities to use this equipment, which addsto the cost of their acquisition and use. Known methods of qualitycontrol and reverse engineering can also require substantial timeinvestments in terms of human time and central processing unit orcomputer time. A need exists to reduce the time, cost, and repeatabilityof quality control sampling and to provide manufacturers a way toreliably and accurately reverse engineer an object.

Certain destructive techniques for capturing both internal and externalfeatures of a physical object also exist. One of these is disclosed incommonly owned co-pending application Ser. No. 08/284,253, filed Aug. 2,1994, now U.S. Pat. No. 5,621,648. Another destructive method andapparatus for capturing the internal and external features of a physicalobject is disclosed in U.S. Pat. No. 5,139,338 which issued to Pomerantzet al. Aug. 18, 1992. Pomerantz discloses apparatus for filling internalcavities in a three-dimensional object and filling the area outside ofan object with a support material solidified to a solid block. Followingsuch solidification, a layer of the entire solid block is removed toallow capture of the features of the exposed surface. The supportmaterial of Pomerantz is required to have generally the same hardness asthat of the object to be analyzed. Further, internal voids in thesolidified material are required to be manually filled by first locatingthe voids and then filling the same in a second step process of encasingthe material. This second process requires that the voids first belocated before they can be filled. Such a step of location requiresfurther effort such as using non-destructive techniques to locate voids.As has been described, the use of such methods and apparatus fordetermining internal features is costly and potentially dangerous.Pomerantz contains no accurate method or apparatus for locating andfilling voids that may exist within the interior structure of the partto be analyzed.

The existence of voids with the interior features of an object to beanalyzed can be extremely detrimental to the accuracy of therepresentation obtained by the apparatus and process. This is especiallytrue if the voids within the interior features of the object areadjacent to those interior features. In such an instance, a voidadjacent a surface internal to the object will create an inaccuraterepresentation of the interior features of the object, and render therepresentation virtually useless, especially for re-creation of asimilar part. A void of filler material adjacent an interior feature ofthe object to be analyzed will appear to be a part of the object, andtherefore render the dimensions obtained from the analysis inaccurate.

It would be desirable to have an apparatus and process for removingvoids within the interior filler material of an object to be analyzed,especially voids adjacent an internal surface area of the object,without undo expense or risk.

Presently, various methods exist for the placement of an object to beanalyzed so as to allow the introduction of a filler material into theinterior and around the exterior of the object. Commonly, a baseplatform or plate has been used, on which the object is placed. InPomerantz, for example, the object is aligned on the base and positionedso that it sits upright. Objects may also be suspended above the plateso that the filling material can completely encase the exterior surfaceof the object. When the encasing material cures, it heats up, alsoheating the part to be analyzed. When the part heats up, it expands, andhas a strong tendency to be forced out of the encasing material.Expansion and contraction of the part creates large forces that theencasing material is incapable of containing.

The advent of the computer and computer aided design (CAD) and computeraided manufacture (CAM) has greatly assisted and expedited the work ofthe engineer and draftsman in designing, drawing, and manufacturingobjects of all kinds. These computer aided engineering tools have madeit possible to design a part and manufacture it without ever goingthrough the prototype development stage. The electronic datarepresenting the drawings of these parts are retained in some form ofmemory, thereby allowing their subsequent access by interested parties.Many parts currently manufactured and sold as well as entire productsare made from engineering drawings that were created before thebeginning of the CAD/CAM era. Some of these drawings have disappeared orbeen destroyed and there is a desire to bring these parts and productsinto the CAD environment.

It would be desirable to have an apparatus and process for taking anexisting object and reproducing it in an electronic medium, therebyallowing pre-CAD/CAM era objects to be incorporated into the electronicenvironment, for providing a less costly alternative quality controlinspection method than is presently available, for reducingmanufacturing costs and speeding products to market, and for enabling anobject to be accurately and quickly reverse engineered.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide new and improvedapparatus that is not subject to the foregoing disadvantages.

It is another object of the present invention to provide method andapparatus for selective removal of predetermined contours of materialfrom an object of interest to expose a surface of interest.

It is still another object of the present invention to provide methodand apparatus for acquiring data relative to each successively exposedsurface of interest.

It is yet another object of the present invention to provide method andapparatus for manipulation of the data relative to a plurality ofexposed surfaces of interest to produce a three dimensional electronicrepresentation of the object of interest for display on a computermonitor, for printing on paper, or for other desired uses.

It is still yet another object of the present invention to providemethod and apparatus for manipulation of the data relative to aplurality of exposed surfaces of interest to produce a surface threedimensional electronic representation of the object of interest fordisplay on a computer monitor, for printing on paper, or for otherdesired uses.

It is another object of the present invention to provide method andapparatus for manipulation of the data relative to a plurality ofexposed surfaces of interest to produce a solid three dimensionalelectronic representation of the object of interest for display on acomputer monitor, for printing on paper, or for other desired uses.

It is still another object of the present invention to provide methodand apparatus for acquiring data relative to an object of interest toprovide quality control data for the manufacturer of the object.

It is still yet another object of the present invention to providemethod and apparatus for substantial elimination of voids within anencasing material and to provide a more accurate representation of theinternal features of an object to be analyzed.

The foregoing objects of the present invention are provided by anapparatus and method for producing three dimensional geometricalmodeling data of an object of interest. The present invention includesmeans for selectively removing a predetermined contour of material fromthe object to produce an exposed surface of interest, apparatus foracquiring data representative of the exposed surface of interest, suchas by scanning the exposed surface of interest, a shuttle for providingrelative movement of the object between the material removal means andthe data acquisition means, and data processing means for converting theacquired data into three dimensional modeling data. In accord with thepresent invention the material removal means may be a face mill. Aprocess for producing the three dimensional geometrical data may includethe steps of encasing the object within a machinable encasing materialto form an encasement; orienting the encasement at a desired orientationrelative to the material removal means; selectively and repeatedlyremoving a predetermined contour of a predetermined thickness from theobject to produce an exposed surface of interest; acquiring datarelative to selected exposed surfaces; converting the exposed surfacedata into perimeter data representative of the surface features at theselected exposed surfaces, both internal and external, of the object;importing the perimeter data into CAD space; and lofting surfaces on theperimeter data to provide a three dimensional surface model of theobject. In an alternative embodiment, the exposed surface data can beconverted into surface data that can be imported into CAD space andconverted into a three dimensional solid model of the object.

To substantially eliminate internal voids in the encasement material,the encasement material may be cured in a series of cycles ofalternating high and low pressure for a predetermined period, followedby a curing at high pressure for another pre-determined period. Thealternating high and low pressure serves to destroy air bubbles or voidswithin the encasement material, especially those present adjacent theinterior surfaces of the object to be analyzed, and provides a moreaccurate and precise representation of the interior features of theobject.

A computer control program for initiating the filling of the mold withan encasement material, the alternating of high and low pressure cyclesin the vacuum chamber, and the acquisition and analysis of encasementlayers is also provided. The computer control program may be used to setthe cycles for high and low pressure, as well as final curing,resolution of encasement material slices, and generation of output filefor the generation of a point cloud representation of the physicalobject.

The foregoing objects of the invention will become apparent to thoseskilled in the art when the following detailed description of theinvention is read in conjunction with the accompanying drawings andclaims. Throughout the drawings, like numerals refer to similar oridentical parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a box diagram illustrating the present invention in its mostsimple conceptual embodiment.

FIG. 2 is a side elevation view of an embodiment of the presentinvention.

FIG. 3 is an end elevation view of the embodiment shown in FIG. 2.

FIG. 4 is a top elevation view of the embodiment shown in FIG. 1.

FIG. 5 is an illustrative example of a representative object that couldbe electronically reproduced in accord with the current invention andshows the object mounted to a machinable support and encased within anencasing material to form a machinable encasement.

FIG. 6 is a partial cross sectional view of the encasement shown in FIG.5 taken along cutting plane 6--6 of FIG. 5.

FIG. 7A, shown on two sheets as FIGS. 7A-1 and 7A-2, is a flow chartillustrating the operation of the embodiment shown in FIG. 2.

FIG. 7B is a flow chart illustrating the processing of the data obtainedusing apparatus in accordance with the present invention for surfacemodeling of the object.

FIG. 7C is a flow chart illustrating the processing of the data obtainedusing the present invention for solid modeling of the object.

FIG. 8 is a schematic diagram illustrating the control system for thepresent invention.

FIG. 9 is a photograph of actual scanned image of an exposed surface ofan illustrative encasement.

FIG. 10 is a photograph of an actual image of a data file after an edgedetection process has been applied to the scanned image of FIG. 9.

FIG. 11 is a photocopy of an actual line art image created by furtherprocessing of the image shown in FIG. 10.

FIG. 12 is a photograph of an actual filtered line art image created byfurther processing of the image shown in FIG. 11.

FIG. 13 is a photocopy of an actual top plan view of a portion of apoint cloud created from the image shown in FIG. 12.

FIG. 14 is a photocopy of an actual image of a plurality of layers ofpoint clouds in three dimensional CAD space created from successivelyexposed surfaces.

FIG. 15 is a photocopy of an actual image of a portion of a spline artdrawing created from the layers of point clouds shown in FIG. 14.

FIG. 16 illustrates the lofting of a surface on the plurality of layersof the spline art drawing shown in FIG. 15.

FIG. 17 shows an encased object mounted for material removal with aplurality of contours of removed material being indicated.

FIG. 18 illustrates a preferred orientation of the object shown in FIG.16 relative to the surfaces to be exposed to increase the data gatheredon a feature of interest.

FIG. 19 is a view of a vacuum chamber with an encased object showntherein.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the present invention is represented in itsbroadest form. Thus, FIG. 1 illustrates an apparatus 10 for creatingthree-dimensional modeling data from an object. Apparatus 10 includes amaterial removal station 12, a data acquisition station 14, and ashuttle 16 providing relative movement of the object of interest to bemodeled between a first position 18 at the material removal station 12and a second position 20 at the data acquisition station 14. It will beunderstood that the stations 12 and 14 could be moved relative to theobject to be modeled and that the present invention contemplates eitherform of relative motion.

The material removal station 12 will include a material removal means 22that selectively and repeatedly removes a predetermined contour ofmaterial from the object of interest to expose a surface of interest.Means 22 could include any of a variety of milling or machining tools,electro-discharge machining (EDM), electrochemical machining (ECM),lasers, or any other equivalent device or method suitable andappropriate for removing the type of material of which the object ofinterest is made. Means 22 will remove a predetermined contour havinglength, width, and thickness and geometry. The length and width of thecontour and the exposed surface will vary depending upon the objectgeometry. For most applications, such as that illustrated herein, auniform thickness of material will be removed; however, the presentinvention contemplates removal of a varying thickness of material withineach contour. Furthermore, for most applications, including thatillustrated herein, after the removal of each contour, the object ofinterest will have an exposed surface of interest that is substantiallyplanar and lies substantially parallel to the previously exposed surfaceof interest. The present invention contemplates, however, the removal ofcontours where the exposed surface has a configuration other thansubstantially planar.

Data acquisition station 14 includes a data acquisition means 24 foracquiring data related to the exposed surface of interest and willinclude means, such as a personal computer (not shown in FIG. 1), forexample, for storing the acquired data and manipulating the data toprovide a three dimensional representation of the object in CAD space.Means 24 may include a scanner, for example, that scans the exposedsurface of interest to create a computer graphic file of the exposedsurface. This file along with others of the subsequently imaged exposedsurfaces will be manipulated in a manner to be described below toproduce the desired model in computer memory for display on a computermonitor, for printing a hard copy of the object of interest on paper, orfor other desired end uses of the user.

Referring now to FIGS. 2-4, an embodiment of the present invention willbe described. It will be understood that the embodiment shown in theseFigures would have the necessary guards and surrounding housing to makethe operation to be described below safe and efficient and that theseitems have been omitted for the sake of clarity in describing andillustrating the present invention. Thus an apparatus 30 in accord withthe present invention may include a face mill 32 for selectivelyremoving predetermined contours of material from an encasement 34.Encasement 34 includes an object of interest 36 (FIGS. 5 and 6)enveloped or encased within a machinable material 38. Machinablematerial 38 may be any material suitable for anchoring the object 36 toa machinable support 40. Thus, material 38 may be an epoxy-type ofmaterial and support 40 may be a wooden, plastic, or similar block. Mill32 includes a cutting head 42 having a plurality of replaceable cuttinginserts 44, only one of which is shown for clarity, for removal of acontour of material from the encasement 34. Cutting head 42 is rotatedby means of a pulley 46 that is driven by a belt 48 extending between itand another pulley 50 rotationally driven by a motor 52. Mill 32 may beof the type manufactured and sold by Sumitomo-Electric. Such a mill canrotate the cutting head 44 at sufficient speeds to cut hard metals, suchas steel, and is also capable of cutting materials such as plastic. Mill32 will be positioned such that cutting head 42 is disposed in anelevated position relative to encasement 34 by a mill support 54comprising a pair of spaced apart upright legs 56 and a horizontalsupport 58, which is broken away for clarity of illustration in FIG. 2.As previously noted, for most applications, herein, after the removal ofeach contour, the object of interest will have an exposed surface ofinterest that is substantially planar and lies substantially parallel tothe previously exposed surface of interest. The exposed surface need notbe planar however. For example, feeding the encasement 34 into the facemill 32 at an angle to the plane of cutting head 42 will create anelliptically shaped exposed surface in the encasement. This exposedsurface can then be imaged by known means and the images analyzed andprocessed in accord with the present invention. The material could alsobe removed in cylindrical layers, such as by a lathe, or in sphericalshells. The exact geometric shape of the removed material can be takeninto account by the appropriate software.

The table or platform 40 on which the encased object 36 sits may also beconstructed of a thermally conductive material. It has been found that athermally conductive table or base 40 upon which the encased object 36sits may be preferable in that it helps to eliminate potentially seriousproblems having to do with the expansion and contraction as the encasingmaterial 38 hardens.

When the encasing material 38 hardens, it heats up. When the materialheats up, heat is transferred to the encased object 36. The objectexpands from the increased heat, and may be likely to be forced from theencasing material 38 by expansion forces. The thermally conductiveplatform or table 40 on which the encasement 34 sits will serve toconduct some of the curing heat of the encasing material 38 away fromthe object 36 so that the object 36 is not subject to forces as strongas those encountered with wooden or plastic platforms 40. The thermallyconductive platform 40 is preferably metal, which will serve to conductheat away from the hardening encasing material 38. The thermallyconductive platform 40 is shown in FIG. 19.

Apparatus 30 will also include a data acquisition station 60 and ashuttle mechanism 62. Shuttle mechanism 62, to be described immediatelyhence, transports encasement 34 between the face mill 32 and the dataacquisition station 60 as well as provides motion perpendicular thereto.Stated otherwise, shuttle mechanism 62 is capable of moving encasementin the x and z directions, where movement in the x direction is ahorizontal movement and movement in the z direction is a vertical motionperpendicular to the x direction of motion. It will be understood thatshuttle mechanisms other than that to be described below arecommercially available for providing motion to a carriage in twoorthogonal directions and that the present invention contemplates theiruse in accord therewith.

To provide x or horizontal direction motion between the face mill 32 andthe data acquisition station 60 a rodless cylinder 64 may beadvantageously utilized. Rodless cylinder 64 may be of the typemanufactured by Industrial Devices Corporation of Novato, Calif. As bestseen in FIG. 2, rodless cylinder 64 includes a housing 66 and a screw 68extending therethrough. Screw 68 is mounted at each end by appropriatebearings (not shown) and is rotationally driven by a power transmissionlinkage 70, such as through an appropriate timing belt or geararrangement, by a motor 72. A nut 74 threadably receives the screw 68and travels in the x direction as the screw 68 is rotated. A carriage 76is attached to the nut 74 by known means such as threaded fasteners andnuts and a mounting block 78 is in turn attached to the shuttle table 76by known means such as threaded fasteners and nuts. The encasement 34 isattached in any known manner, such as bolting, to the mounting block 78.As screw 68 is rotationally driven by the motor 72, therefore, nut 74and consequently encasement 34 will travel in a horizontal or xdirection between the face mill 32 and the data acquisition station 60as indicated by double-headed arrow 79.

To provide motion in the z or vertical direction, rodless cylinder 64 isattached at its ends 80, 82 to carriages 84, 86 respectively, each ofwhich in turn forms part of an upright oriented rodless cylinder 88, 90,respectively. In this manner rodless cylinder 64 functions as a frame tosupport the shuttle table 76, the mounting machinable block 78 and theattached encasement 34 during the vertical motion. Rodless cylinders 88and 90 are similar to rodless cylinder 64 and may also be of the typemanufactured by Industrial Devices Corporation of Novato, California.Because of their similarity, only rodless cylinder 90 will be describedfurther. Thus, rodless cylinder 90 also includes a housing 92 and ascrew 94 rotationally mounted by appropriate bearings (not shown) andextending therethrough. The screw 94 is rotationally driven by a powertransmission linkage 96, such as through an appropriate timing belt orgear arrangement, by a motor 98. A nut 100 threadably receives the screw94 and is attached by known means such as threaded fasteners and boltsto carriage 86. Thus, as seen in FIG. 2, as screws 94 are rotationallydriven by motors 98, nuts 100 will be raised or lowered in the verticalor upright direction, thereby carrying rodless cylinder 64 therewiththrough its attachments to carriages 84 and 86. Rodless cylinder 64 maybe moved from its position shown in FIG. 1 to the position 102 shown inphantom outline as the material removal operation proceeds as indicatedby double-headed arrow 104. The motions of the rodless cylinders 88, 90will be appropriately coordinated so as to ensure that the rodlesscylinder 64 is lifted uniformly at its ends, thereby further ensuringthat encasement 34 will be fed into the cutting head 42 at the sameangle with each successive pass. This method of operation simplifies thedata acquisition and processing but is not critical to the presentinvention since contours of varying geometries, including thicknessescan be removed so long as the data processing means is appropriatelyprogrammed to address these geometry changes.

Shuttle mechanism 62 also includes an x-motion sensor 106 and a z-motionsensor 108 and respective flags 110 and 112. Sensors 106 and 108 may beany known type of sensor, such as an infrared photo-Darlington type ofsensor. These sensors aid in the control of the motion of the shuttletable 76 by relaying a signal to a control means, such as a computer,when the motion of the shuttle 62 reaches its a predefined position, aswill be explained in greater detail below.

Data acquisition station 60 includes a data acquisition device 114supported in an elevated position above rodless cylinder 64 by two pairsof spaced apart support legs 116, 118. Device 114 may be a scanner ofthe type manufactured by UMAX Data Systems, Inc. This type of scanner iscapable of achieving a resolution of 1200 dots per inch, which willnormally be beyond the resolution (less than 0.001 inch) necessary forachieving the desired accuracy in object dimensions. While thisresolution or even greater resolutions can be utilized, in mostapplications this will simply increase the data processing time withlittle or no real gain in object dimension accuracy.

Referring now to FIGS. 5 and 6, an object 36 is shown encased within anencasing material 38 to form an encasement 34. With some objects it maynot be necessary to completely encase the object such as that shown inthe Figures. It is generally desirable to do so, however, for severalreasons. First, where an object may have features such as a dependingflange or other member, that is, stalactite-like features, as the objecthas material contours removed by the face mill 32 the flange or otherdepending member will be left without any support and will becomeseparated from the remaining portion of the object unless some supportis provided for it, a function satisfied by the encasing material.

Secondly, the encasing material, which is applied so as to completelyfill any internal volumes, supports all of the surfaces duringmachining, milling, or material removal operations and thereby inhibitsthe formation of burrs on the edges of the object as the contours areremoved.

Third, by appropriately selecting an encasing material such that it hasa different color or shade of gray from that of the exposed surface ofinterest, the scanner and thus the computer later manipulating the datais provided with a contrast between the exposed surface of the encasingmaterial and the exposed surface of interest that facilitates the datamanipulations that occur later in the process. Stated otherwise, properselection of the encasing material provides a high visual contrastbetween the object surface and the encasing material surface whichenables a line of demarcation to be determined between the surfaces.

Preferably the encasing material will have a reflectance that issubstantially different from that of the exposed surface of interest,thereby providing the high contrast. The normal reflectance of a surface"is a measure of the relative brightness of the surface when viewed andilluminated vertically. Such measurements are referred to as a`perfectly white Lambert surface`--a surface which absorbs no light, andscatters the incident energy isotropically--and are usually approximatedby magnesium oxide (MgO) or some other bright powder." McGraw-HillConcise Encyclopedia of Science and Technology ©1984, page 49. The ratioof the normal reflectance of the exposed surface of interest R_(o) tothat of the normal reflectance of the encasing material R_(e) should besuch that the ratio R_(o) /R_(e) is as great as possible as a rule. Forexample, when aluminum is milled by a face mill, a shiny, silveryexposed surface is produced. An encasing material such as a black epoxymixture is advantageously used to form the encasement since thisencasing material will provide a dark exposed surface when machined,thereby providing a high contrast with the exposed aluminum surface. Thehigh contrast increases the sharpness of the image scanned because theperimeter of the object of interest is more sharply defined relative tothe encasing material.

Finally, the use of an epoxy or epoxy-like material as an encasingmaterial provides a simple and rapid method of attaching the object 36to the machinable support 40.

OPERATION OF THE PRESENT INVENTION

With the foregoing description in mind, the operation of the apparatus30 in accord with the present invention can be described with referenceto the Figures, and particular FIGS. 7-8. The general operation of thepresent invention will be first explained with reference to FIGS. 7A-1and 7A-2. The conversion of the acquired data into a surface model willthen be explained with reference to FIG. 7B. Finally, a discussion ofthe conversion of the data relative to FIG. 7C will be undertaken.First, an object of interest whose internal and external geometry isdesired to be reproduced in an electronic medium is selected asindicated at 200. The object of interest is appropriately cleaned asindicated at 202 and then encased in the preselected encasing materialas indicated at 204 to form the encasement 34. The encasement 34 canthen be mounted to the support 40 as indicated at 206. As previouslydiscussed, the encasing material can also serve to mount the object 36to the support 40, in which case steps 204 and 206 are combined into asingle step. The encasing step, whether separate or joined with themounting step, should be accomplished such that the encasing materialfills all internal volumes of the object of interest and engages allsurfaces, internal or external thereof, thereby forming the encasement34. The encasement process will be discussed further below. As will alsobe discussed further below, at this time if there is a particularfeature of interest in the object, it should be identified as indicatedat 208 in phantom since it may be desirable to select a particularorientation of the object on the support so that the feature of interestis disposed at a predetermined orientation to the cutting plane of theface mill 32. After the encasement 34 is mounted as desired to thesupport 40, the support 40 will be attached to the mounting block 78using conventional techniques such as screws 120, which are best seen inFIG. 4, as indicated at 210.

The encasement process may be made more effective by further limitingthe presence of voids in the hardening encasing material 38. In someencasement processes, voids are left in the encasing material 38.Particularly troublesome are voids adjacent the surface of the object 36that is being encased, since such voids could be interpreted wrongly asa part of the object 36.

It has been found that to more effectively limit voids in the encasingmaterial 38, a vacuum chamber 310 may be used. The vacuum chamber 310 isbest shown in FIG. 19. The object 36 is encased in encasing material inthe normal fashion. Following this, or during the encasement process,the object and encasement are placed in vacuum chamber 310. While invacuum chamber 310, the object 36 and encasing material 38 are subjectedto alternating cycles of high and low pressure during the curing phaseof the encasing process. The cycling high and low pressures are used fora preferred period of approximately 20 minutes, although longer cyclesmay be used. The ultimate determination of the cycle time will bedetermined largely by the curing time of the encasement material 38.Similarly, the time at which vacuum chamber 310 is held at high and lowpressure is variable.

The high and low pressure values used during the curing process areapproximately sixty pounds per square inch and near vacuum,respectively. The high and low pressures are alternated throughout thecuring period. The high and low pressure cycles are repeated atintervals of approximately two minutes, followed by a final highpressure curing period of approximately ninety minutes. This highpressure curing time may also be adjusted depending on the encasementmaterial 38 to be used.

As has been mentioned, the curing period will be dependent on the typeof encasing material 38 used for the encasement process. For example,when encasing large objects 36, it may be necessary to begin the curingstage of the encasement process before the part or object 36 is fullycovered with encasing material 38. When this is the case, the high andlow pressure cycling may be performed throughout the encasement process,which may take 24 hours or more.

All functions relating to the curing process may be performed bysoftware controlling the appropriate functions.

After the encasement 34 and support 40 have been attached to themounting block, various physical parameters of the encasement will beobtained, including the height, length and width of the encasement, aswell as its weight as indicated at 212. This step may be taken ifdesired before the encasement is mounted to the machinable support at206. The weight of the encasement 34 is important since this factor willenter into the acceleration and deceleration of the shuttle table 76.This information will be entered into computer 214 (FIG. 8) or likecomputational means containing an appropriate microprocessor. The feedspeed, that is, the rate at which the shuttle table 76 is translated inthe x-direction into the face mill 32 for contour removal, is determinedand entered into computer 214 as indicated at 216. The feed speed willvary depending principally on the material out of which the object 36 ismanufactured. For harder materials, such as steel, aluminum, and othermetals, the feed speed will be less than where the object ismanufactured of, say, a synthetic material such as nylatron. Otheroperational parameters will be determined, such as the desired contourthickness as indicated at 218 and the scan pixel density as indicated at220, and will be entered into computer 214.

With the foregoing information, the computer 214 can begin materialremoval and data acquisition according to a previously arranged program.Thus, referring now to FIGS. 7 and 8, the computer 214 will send theappropriate signals to the z-drive motors 98 for rodless cylinders 88and 90 over the appropriate communication link 222. These signals willthereby cause the screws 94 in cylinders 88, 90 to rotate and carry theshuttle table 76 and, more specifically, rodless cylinder 64 downwardlyto its z-home position as shown in FIG. 1 and as indicated at 224 inFIG. 7A-1. As the rodless cylinder 64 is lowered, flag 112 will break alight beam generated by the z-motion sensor 108, thus providing a signalto computer 214 over an appropriate communication link 226 that therodless cylinder 64 has reached its home position. The computer 214 willthen provide the appropriate signal to z-drive motors 98 to stop.

The computer will next send a signal over an appropriate communicationlink 228 to x-drive motor 72 to cause the shuttle table 76 to betranslated in the x-direction to its x-home position as indicated at 230as indicated at FIG. 7A-2. Once again, as the shuttle table 76approaches the x-home position, flag 110 will break a beam produced byx-motion sensor 106, thereby providing a signal to computer 214 over anappropriate communication link 232. Computer 214 will then send theappropriate signal to x-direction motor 72 over communication link 228to stop, thus ceasing the translation of the shuttle table 76 in thex-direction.

Using the encasement dimensions previously supplied at 212, the computer214 may determine an encasement specific predefined pre-cutting positionin the x-direction, or if desired, such a pre-cutting position in thex-direction can be defined once for all objects. The computer 214 willthen send the appropriate signal to x-direction motor 72 to move theshuttle table 76 to the predefined pre-cutting position as indicated at234. The computer 214 will then command the operation of the z-drivemotors to raise the shuttle table 76 to a z-cutting height as indicatedat 236. Like the pre-cutting position in the x-direction, this z-cuttingheight can be calculated based upon the height of the encasement enteredinto the computer 214 as indicated at 212, or it can be established forall encasements. Preferably, this height should be such that the topmostportion of the encasement 34 is near the cutting plane defined by therotation of the cutting inserts 44 of face mill 32. It is preferablethat the encasement 34 be disposed too low such that no material beremoved from the encasement on the first and subsequent passes throughthe face mill 32 than it is to have the encasement disposed too high andremove too thick a contour of material. Removing too thick a contour onthe first pass could result in the loss of object geometry and/oroverload the face mill 32 and perhaps cause a mechanical breakdown ofthe mill.

When the shuttle table 76 is in the predefined, pre-cutting position inboth the x- and z-directions, computer 214 will send a signal over anappropriate communication link 238 to face mill motor 52, commanding themotor 52 to start the rotation of the cutting head 42 as indicated at240. When the cutting head 42 is rotating at the desired speed, thecomputer will then again command the x-direction drive motor 72 totranslate shuttle table 76 and attached encasement 34 into face mill 32at the predetermined feed speed, as indicated at 242. Mill 32 willremove an initial contour of material to expose a surface C1 as seen inFIG. 6.

After removal of the initial layer of material from the encasement 34,the shuttle table 76 will be lowered by the appropriate command fromcomputer 214 to z-drive motors 98 as indicated as 244. The shuttle table76 will then be translated in the x-direction to the x-home position asindicated at 246. During this translation, as the shuttle table 76 nearsthe x-home position it will pass a Hall-effect switch (not shown) thatwill provide a signal to the computer 214 that the shuttle table 76 isnear the home position. The computer 214 will then decelerate theshuttle table 76 so that it is translating at a slow rate of speed. Asthe shuttle table 76 "enters" the x-home position, flag 110 will breakthe light signal generated by x-sensor 106. Sensor 106 will provide asignal to computer 214 which will in turn command the x-drive motor 72to stop. Computer 214 may then command the x-drive motor to reverse andslowly back the shuttle table 76 away from the x-home position untilflag 110 no longer breaks the light signal of sensor 106. Translation inthe x-direction will then cease and the shuttle table 76 will be broughtto an immediate stop. In this way it will be possible to repeatedly andreliably position the shuttle table 76 and the encasement 34 in the samex-position after each material removal pass.

The computer 214 will next command the z-drive motors to raise theshuttle table 76 until the exposed surface C1 is substantially flushwith the glass of the scanner 114 as indicated at 248. Computer 214 willthen command scanner 114 over an appropriate communication link 250 toscan the newly exposed surface as indicated at 252. After the scanningis complete, the shuttle table 76 will be lowered as indicated at 254and the cycle repeated from step 234, with successive contours ofencasement being removed, such as layers C2-C7 as shown in FIG. 6, withthe thickness of each contour being determined at step 218. Thus, as theshuttle table 76 is raised into cutting height with each pass, thethickness of the material removed on the previous pass will be added tothe last height of the shuttle table so that the face mill consistentlyremoves the same thickness of material. This cycle of material removaland scanning will continue until the face mill 32 has completely milledaway the encasement 34. With the example shown in FIGS. 5 and 6, object36 has a substantially planar upper surface, thus necessitating theremoval of several contours, specifically C1-C5, before any objectmaterial is removed. It will be seen that as contour C6 was removed, alayer of material 256 was removed and that as contour C7 was removed, alayer of material 258 was removed, each removal exposing a surface to bescanned.

Referring now to FIGS. 7B and 9-15, the processing of the scanned imagesof the exposed surfaces of encasement 34 will be described. It will beunderstood that the thickness of the contour removed with each passthrough the face mill 32 can be precisely controlled such that a contourhaving a thickness as small as 0.001 inch can be removed. It will befurther understood that if desired, a series of passes can be madethrough the face mill 32 before a particular exposed surface is scannedby scanner 114. Or if desired, a scan can be made after each pass andeach scan or only selected scans can be further processed as describedfurther herein. FIG. 9 shows a photocopy of an actual scanned image 260like that produced by commercially available scanners such as scanner114. Image 260 shows the exposed surface 262 of the object 36 and theexposed surface 264 of the encasing material, the geometry of thisparticular representative object 36 perhaps best being understood byviewing FIGS. 5 and 6 in conjunction with FIG. 9. Scanned image 260 isprocessed as indicated at 266 in FIG. 7B to define the edges of theobject 36, thus yielding image 268 as shown in FIG. 10, where theperimeter of the object 36 is indicated with reference numeral 269. Thisprocess, known in the art as "edge find" can be accomplished by acommercially available software package sold by Micrografx under theDesigner trademark. This process creates a raster curve over areas ofvisual contrast, such as that found between the exposed surfaces 262 and264 of object and encasing material, respectively, and succeeds indefining an edge 270 that delineates the boundary of visual contrastbetween the object 36 and the encasing material 38.

The "edge find" image 268 can then be processed as indicated at 272 toproduce a line art image 274 as seen in FIG. 11. This process can alsobe accomplished by the Designer software. This process removes allshades of gray, as can be seen by comparing FIGS. 9 and 10 with FIG. 11,and produces a simple black and white image of raster lines and curves.

The line art image 274 can be further processed as indicated at 276 toproduce a filtered line art image 278 as seen in FIG. 12. This processfunctions to filter out noise and to retain only legitimate features ofthe original image such as the edges. During this process the featuresof one image are compared with those above and below it on the z axis.Noise will not generally appear at the same location from one image tothe next and will be filtered out of the image by the software. As canbe seen by comparing images 274 and 278 of FIGS. 11 and 12,respectively, filtered line art image 278 is much "cleaner" than is lineart image 274.

Referring now to FIGS. 7B and 13, the processing of the scanned imageswill be further explained. Thus, the filtered line art image 278 will beprocessed as indicated at 280 in FIG. 7B to produce a point cloud image282 as seen in FIG. 13 in an enlarged view. During this process, as willbe understood, the filtered line art image comprises a raster imageformed of pixels. These pixels each define an area. The line art imageto cloud point image involves converting each of the pixels to a pointhaving a defined position in xy space. Stated otherwise, this process isa raster to vector transformation process and in well known computerlanguage involves converting a raster file in a format known as TIFF toa vector file known as DXF. This conversion can be accomplished by theDesigner software package sold by Micrografx. The previously discussedimage processing steps can also be performed by software available forAldus.

The next step in the data processing process will involve assigning az-value to each point in the point cloud layer such that each point isnow located in xyz space, as indicated at 284. This "assignment" ofz-values is necessary since as the exposed surface of the encasement 34is scanned, a two dimensional image in xy space is created. Without theassociated z-values, the images would exist in a single plane in CADspace. There is no inherent data representative of the elevation of theparticular exposed encasement surface as a result of the scanning. Thisinformation will be associated with the scanned image by informationprovided by a pulse counter (not shown in the Figures) associated withthe z-drive motor. The count from the pulse counter is secured at thetime each scan is made and is retained to identify the z-value orelevation of that particular scan. The point cloud layer images are thenimported into CAD space as indicated at 286. This process can beaccomplished by a commercially available software package sold byImageware of Ann Arbor, Mich., under the Surfacer trademark. Eachimported point cloud layer images represents a particular exposedsurface of the object 36. The layer images can then be "stacked" oneupon the other in CAD space as indicated by FIG. 14, which shows foursuch layers, 288a, 288b, 288c and 288d.

The point cloud layers can then be processed to produce a spline artimage. This can be accomplished with the aforementioned Surfacersoftware package and involves fitting curves--called splines--ofpredefined length through the points in each point cloud layer asindicated at 290 and as shown in FIG. 15 wherein layers 288a-d have beenprocessed to produce layers 292a, 292b, 292c, and 292d, respectively,thus effectively defining the perimeter edge of the object 36 withineach layer.

The final step as indicated at 294 involves lofting a surface on thestack of spline art layers to produce a surface model such as that shownin FIG. 16. This process can also be accomplished with the Surfacersoftware package as well as others that are commercially available. Theresulting surface model includes the external features of the object aswell as the much desired internal features, such as the hole 296 shownin FIG. 16. Where the removed contours have a thickness of, say 0.010inch, and where each exposed surface is scanned, the layers shown inFIG. 15 and the surface shown in FIG. 16 will have a depth substantiallyequal to 0.030 inch. It will be understood that the foregoingrepresentations show several stacked data layers whose thickness isdetermined by the thickness of the layers of material removed with eachpass through the material removal means as well as the scanningfrequency, that is, whether a scan is made with each cutting passthrough the encasement 34 and whether each scan is in fact processed aspart of the object reconstruction in CAD space.

Alternatively to producing a surface model of the object of interest,the scanned images can be processed to produce a solid model in threedimensional CAD space. Referring now to FIG. 7C, this process will bedescribed. The first step of this process will involve processing thescanned images to convert the pixel data produced by the scans intolayered point clouds representative of the object of interest asindicated at 298. From there, a surface will be lofted onto each pointcloud layer, as indicated at 300. A z-value will be assigned to eachlayer as indicated at 302. The layers can then be imported into CADspace and stacked as indicated at 304. As a final step as indicated at306, a solid will be created between two adjacent layers and the processwill be repeated until a solid is formed between all adjacent layers.

Referring now to FIGS. 17 and 18, a method of orienting the object ofinterest relative to the cutting plane of the material removal meanswill be discussed. With certain objects, there may be a particularfeature whose position within the object is very important to determineprecisely. Thus, as seen in FIG. 17, an encasement 130 comprising anobject of interest 132 encased within an encasing material 134 andmounted to a machinable support 136 is shown. Object 132 includes a hole138 extending partially therethrough. Hole 138 has a bottom surface 140.Many objects have a somewhat orthogonal configuration that naturallyleads to mounting the object squarely on the machinable support in muchthe same manner that object 132 is shown mounted in the Figure. Alsoshown in the Figure are the various surfaces 142a-m of the object thatwill be exposed as a result of the material removal process. It can beseen that bottom surface 140 of hole 138 lies substantially parallel tothe exposed surfaces. Thus, by orienting the object 132 in the fashionshown wherein a planar surface of interest is disposed parallel with thecutting plane of the material removal means, information as to the truedepth of the hole 138 will be lost since the removal of the contour thatexposes surface 142m will not reach the bottom 140 and removal of thefinal contour of material will also result in removal of the feature.

Referring now to FIG. 18, a preferred orientation for an object having afeature of interest is shown. Thus, an encasement 144 comprising anobject 132 encased within an encasing material 146 and mounted to amachinable support 136 is shown. Also indicated in the Figure are thesuccessively exposed surfaces 148a-p. With the orientation of object 132within encasing material 146 as shown, the feature of interest, that is,hole bottom 140, is oriented such that its planar bottom lies at anangle to the exposed surfaces 148a-p; that is, it lies at an angle tothe cutting or material removal plane of the material removal means.With this orientation, information regarding the depth of hole 138within object 132 is revealed by successively exposed surfaces 148j-p.With this many exposed surfaces defining the hole bottom 140, theaforementioned data manipulation process can accurately reproduce thefeature of interest at the correct location within the part. Thus, wherean object to be modeled by the present invention includes a particularfeature of interest, the object should be oriented such that it lies atan angle to the material removal plane of the material removal means.

The foregoing description of the present invention thus contemplates thesuccessive removal of layers of material of predetermined thickness froman object. The thickness of the removed material may be as small as thematerial removal means is capable. The present invention contemplatesscanning selected exposed surfaces. All such surfaces may be scanned ifdesired. The present invention further contemplates that successivepasses through the material removal means wherein varying thicknesses ofmaterial are removed with each pass. For example, where it is desired toscan an exposed surface at every 0.01 inch and to construct a model fromsuch scans, a plurality of passes through the material removal means maybe made wherein a first pass might remove a contour having a thicknessof, say, 0.006 inches, a second pass might remove a contour having athickness of, say, 0.003 inches, and a third and final pass might removea contour having a thickness of, say, 0.001 inch for a total thicknessof material removed of 0.01 inch. Furthermore, preselected surface scansof specific z-values may be scanned and analyzed. That is, it may beeasily and readily recognized that through a certain portion of anencasement that scans every 0.01 inch, for example, would be sufficientbut that in other portions it would be desirable to scan every 0.005inch, for example. In such a circumstance the apparatus could be set upto remove contours having a thickness of 0.005 inches throughout theencasement while scanning at 0.005 inches only in the latter portion andat 0.01 inches in the remaining portion. Or each layer at 0.005 inchescould be scanned but in the processing only those in the latter portionwould be processed at 0.005 inches while in the former portion everyother scan would be processed to yield layers 0.01 inch apart. Finally,the system could be configured to mill in the former portion at 0.01inch and in the latter at 0.005 inch and all scans could be evaluated.

The present invention having thus been described, other modifications,alterations, or substitutions may now suggest themselves to thoseskilled in the art, all of which are within the spirit and scope of thepresent invention. For example, the encasing material could be dyedwater or other similar low viscosity type of material. In thisembodiment the object of interest would be immersed in the dyed water,which would then be frozen. The material removal would then occur in acold system; that is, one maintained at such a temperature that theencasing material would be maintained in a frozen state. Such a processwould provide several advantages, among them an assurance that internalvoids would be filled, ease of object preparation, and that the residualwaste products from the material removal operation would be non-toxicand easily cleaned up. Alternatively, the encasing material couldcomprise a form of matter that radiates, such as a phosphor, which wouldtransmit its radiative signature, which may be visual, to theappropriate sensor designed to detect such radiation. The radiationprovided by the encasing material would provide a high contrast betweenit and the object since the object would be non-radiating. It istherefore intended that the present invention be limited only by thescope of the attached claims below.

What is claimed is:
 1. Apparatus for producing electronic datarepresentations of an object, the object being formed from at least onematerial, said apparatus comprising:a material removal station; a datagathering station; and a shuttle providing relative movement of theobject between said stations;wherein said material removal stationcomprises:means for removing a predetermined contour of material fromthe object; wherein said shuttle comprises:a table for holding theobject; and means for providing relative movement of said table betweensaid material removal station and said data gathering station; andwherein said data gathering station comprises:means for successivelyimaging the object after removal of a predetermined contour; and meansfor storing data gathered by said means for imaging; and wherein saidtable is thermally conductive.
 2. An apparatus as described in claim 1,wherein said table is metal.
 3. An apparatus as described in claim 1,and further comprising:a variable pressure chamber surrounding saidshuttle, whereby the object may be subjected to varying pressures.
 4. Anapparatus described in claim 3, wherein the object is encased, whilesaid shuttle is in said variable pressure chamber, within an encasingmaterial to form an encasement and wherein the contour removing meansremoves a pre-determined contour of the encasement.
 5. An apparatus asdescribed in claim 4, and further comprising:means for encasing theobject in the encasing material without the object contacting saidtable.
 6. A method for producing electronic data representations of anobject having a plurality of surfaces, said method comprising:encasingthe object within a preselected encasing material to form an encasement,such encasing being done so that all surfaces of the object are coatedwith the encasing material and so that the encasing materialsubstantially fills all interior volumes of the object; removing apredetermined contour from the encasement so as to expose an encasementsurface; acquiring an electronic representation of selected exposedencasement surfaces after a predetermined contour has been removed;processing each electronic representation to create a predeterminedelectronic representation of each said encasement surface; and curingsaid encasing material in a vacuum chamber in which a pre-determinedpattern of high and low pressure cycles is used.
 7. A method asdescribed in claim 6, wherein the step of curing said encasing materialcomprises the steps of:lowering the pressure in the vacuum chamber tonear vacuum, and raising the pressure in the chamber to high pressure,in a series of cycles for approximately 20 minutes; and finally curingsaid encasing material at high pressure for a pre-determined curingperiod.
 8. A method as described in claim 7, wherein said pre-determinedcuring period is approximately 90 minutes.
 9. A method as described inclaim 7, wherein said high pressure is approximately 60 psi.
 10. Amethod as described in claim 7, wherein the pressure in the chamber isalternated between high and low throughout the curing period.
 11. Amethod as described in claim 7, wherein said curing is approximately 24hours.
 12. A method for creating a point-cloud representation of aphysical object, comprising the steps of:suspending the object above abase in a mold; filling the mold with an encasing material to create anencasement; placing the mold in a vacuum chamber; curing the encasingmaterial in the vacuum chamber at alternating high and low pressure fora pre-determined length of time; removing the encasement from the mold;removing a pre-determined contour of the encasement so as to expose anencasement surface; acquiring an electronic representation of selectiveexposed encasement surfaces after a predetermined contour has beenremoved; and processing each electronic representation to create apre-determined electronic representation of each said encasementsurface.
 13. A method as described in claim 12, wherein said curing stepincludes the steps of:lowering the pressure in the chamber to nearvacuum, and raising the pressure in the chamber to high pressure, in aseries of cycles for approximately 20 minutes; and finally curing saidencasing material at high pressure for a pre-determined curing period.14. A method as described in claim 13, wherein said pre-determinedcuring period is approximately 90 minutes.
 15. A method as described inclaim 12, and further comprising:cleaning the object before suspendingthe object above the base in a mold.
 16. A method as described in claim12, and further comprising:measuring the length, width, and depth of theencasement after removing the encasement from the mold.
 17. A method asdescribed in claim 12, wherein the step of removing a pre-determinedcontour of the encasement includes choosing a thickness for thepre-determined contour to be removed.
 18. Apparatus for producingelectronic data representations of an object, the object being formedfrom at least one material, said apparatus comprising:a material removalstation; a data gathering station; and a shuttle providing relativemovement of the object between said stations;wherein said materialremoval station comprises:means for removing a predetermined layer ofmaterial from the object; wherein said data gathering stationcomprises:means for successively imaging the object after removal of apredetermined layers; and means for storing data gathered by said meansfor imaging; and wherein said shuttle comprises:a thermally conductivetable for holding the object; means for moving said table in a firstsubstantially linear direction between a first position in which saidtable is at said data gathering station in imaging alignment with saidmeans for successively imaging the object, and a second position inwhich said table is at said material removal station in materialremoving alignment with said means for removing a layer of material; afirst sensor for determining when said table is at said data gatheringstation in imaging alignment with said means for successively imagingtile object; means for moving said table in a second directionsubstantially perpendicular to said first direction into and out ofrelative material removing engagement with said means for removing apredetermined layer of material; and a second sensor for determiningwhen said table is at said material removing station in relativematerial removing engagement with said means for removing material.